Light emitting device

ABSTRACT

A light emitting device includes a base including a support having a support surface. A light emitting element includes a semiconductor layer and a sapphire substrate provided on the semiconductor layer opposite to the support surface. A light-transmissive covering member is provided on the sapphire substrate to sandwich the sapphire substrate between the semiconductor layer and the reflecting film. A light emitted from the semiconductor layer is configured to be extracted from the sapphire substrate between the semiconductor layer and the reflecting film. A height of the light-transmissive covering member viewed in a direction in which a width of the light-transmissive covering member appears smallest is 0.5 times or less of the width of the light-transmissive covering member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of the U.S. patentapplication Ser. No. 16/111,239, filed Aug. 24, 2018, which is acontinuation application of the U.S. patent application Ser. No.15/387,649, filed Dec. 22, 2016, which issued as U.S. Pat. No.10,090,441, which claims priority under 35 U.S.C. § 119 to JapanesePatent Application No. 2015-249237, filed Dec. 22, 2015. The contents ofthese applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a light emitting device.

Discussion of the Background

In recent years, various electronic components have been proposed andput into practical use, and high performance has been required of theseelectronic components. For example, in backlights used for liquidcrystal televisions, general lighting devices, and the like, well-shapedlight emitting devices are appreciated due to a demand of reduction inthickness, so that reduction in size of a light emitting device itselfis highly demanded.

For example, Japanese Unexamined Patent Application Publication No.2006-114863 discloses a light emitting device that realizes batwinglight distribution characteristics by combining a secondary optical lenswith an LED and enables reduction in thickness of equipment by uniformlydiffusing light in a short irradiation distance.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a light emittingdevice includes a base, a light emitting element, a reflecting film, anda light-transmissive covering member. The base includes a support havinga support surface, and a conductive wiring provided on the supportsurface. The light emitting element is mounted on the conductive wiringand the support surface to be electrically connected to the conductivewiring. The light emitting element includes a semiconductor layer and asapphire substrate. The semiconductor layer is provided on theconductive wiring and the support surface. The sapphire substrate isprovided on the semiconductor layer opposite to the support surface. Thereflecting film is provided on the sapphire substrate to sandwich thesapphire substrate between the semiconductor layer and the reflectingfilm, a light emitted from the semiconductor layer being configured tobe extracted from the sapphire substrate between the semiconductor layerand the reflecting film. The light-transmissive covering member isprovided on the support surface to cover the light emitting element anda covered region on the support surface except for an uncovered regionon the support surface. A height of the light-transmissive coveringmember viewed in a direction in which a width of the light-transmissivecovering member appears smallest is 0.5 times or less of the width ofthe light-transmissive covering member. An average reflectivity in theuncovered region of the base with respect to a peak emission wavelengthof light emitted from the light emitting element is higher than anaverage reflectivity in the covered region of the base with respect tothe peak emission wavelength of light.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic top view illustrating a part of a light emittingdevice according to a first embodiment;

FIG. 2 is a schematic sectional view taken along the line A-A in FIG. 1;

FIG. 3 is a schematic top view illustrating an example of the wholestructure of the light emitting device of the first embodiment;

FIG. 4 is a schematic sectional view illustrating a part of a lightemitting device according to a second embodiment;

FIG. 5 is a schematic sectional view illustrating a part of a lightemitting device according to a third embodiment;

FIG. 6 is a schematic sectional view illustrating a part of a lightemitting device according to a fourth embodiment;

FIG. 7 is a schematic sectional view illustrating a part of a lightemitting device according to a fifth embodiment;

FIG. 8 is a schematic top view illustrating a light emitting deviceaccording to Example 2;

FIG. 9 is a schematic sectional view illustrating the light emittingdevice according to Example 2;

FIG. 10 is a graph showing light distribution characteristic of a lightemitting device according to Example 1; and

FIG. 11 is a graph showing light distribution characteristic of thelight emitting device according to Example 2.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

Hereinafter, best modes and detailed descriptions for practicing thepresent invention are described in detail with reference to drawings.The modes indicated below, however, are examples of the light emittingdevice for embodying technical ideas, and the embodiments of presentinvention is not limited to the ones described below.

First Embodiment

As illustrated in FIGS. 1, 2, and 3, a light emitting device accordingto a first embodiment mainly includes a base 120 having a support member101 and a conductive wiring 102 formed on the support member 101; alight emitting element 105 mounted on the base 120 and electricallyconnected to the conductive wiring 102; and a light-transmissivecovering member 108 covering the light emitting element 105 and a partof the base 120.

FIG. 2 is a schematic sectional view taken along the line A-A in FIG. 1.As illustrated in FIG. 2, the light emitting element 105 includes areflecting film 122 on an upper surface of the light emitting element.Among the surfaces of the light emitting element 105, the upper surfaceof the light emitting element 105 refers to a surface disposed on a base120 side, and hereinafter also referred to as a “first surface”. Asurface opposite to the first surface hereinafter referred to as a“second surface”. The light emitting element 105 includes a plurality oflateral surfaces between the first surface and the second surface.

The base 120 includes the support member 101 made of an insulatingmember and the conductive wiring 102 formed on a surface of the supportmember 101. As illustrated in FIG. 2, the light emitting element 105 isflip-chip mounted so as to straddle a pair of positive and negativeconductive wirings 102 a and 102 b provided on an upper surface of thesupport member 101 with a bonding member 103 interposed between thelight emitting element and the pair of conductive wirings. An underfillmaterial 106 may be disposed in a gap between a lower surface of thelight emitting element 105 and an upper surface of the base 120, or on alateral surface of the light emitting element 105.

A light reflecting layer 104 made of an insulating member is formed in aregion of the conductive wiring 102 which does not require electricalconnection. The covering member 108 can be a light-transmissive memberand can be provided on an upper surface of the base 120 so as to coverthe light emitting element 105. The covering member 108 may be in directcontact with the base 120. The viscosity of the covering member 108 isadjusted so as to enable printing or dispenser coating, and the coveringmember can be cured by heating or light irradiation. The covering member108 may be formed into, for example, a substantially hemisphericalshape, a vertically long protrusion shape in a sectional view, and acircular shape or an elliptical shape in a top view.

On the upper surface of the base 120, the average reflectivity in aregion not covered with the covering member 108 (i.e., an uncoveredregion) is set higher than the average reflectivity in a region coveredwith the covering member 108 (i.e., a covered region). Generally, thevicinity of the light emitting element 105 is covered with a reflectinglayer in order to efficiently extract the light from the light emittingelement 105. The light reflected in the vicinity of the light emittingelement, however, is extracted from directly above the light emittingelement 105, therefore the luminance is increased in a place where theluminance is desired be decreased to obtain uniform light emission.

Therefore, in the present embodiment, the average reflectivity for thelight emission peak wavelength of the light emitting element in theregion of the base covered with the covering member 108 is set lowerthan the average reflectivity for the light emission peak wavelength ofthe light emitting element in the region positioned outside the coveringmember, in order to decrease the quantity of light reflected in aboundary surface between a bottom surface of the covering member and theupper surface of the base. Thereby, an influence of diffusing reflectionof light in the covering member 108 can be decreased to reduce lightthat passes through the covering member upwardly.

The term “average reflectivity” in the present specification refers to avalue obtained by averaging the reflectivities of members in a region,whose reflectivity is desired to be measured, in consideration of theratio of the areas of the members.

For example, the reflectivity of a groove 130 (see FIG. 1) between thepair of conductive wirings 102 a and 102 b may be set higher than thereflectivity of the upper surface of the conductive wiring 102.

The reflectivity can be measured by a spectral reflectivity measuringdevice. Although reflectivity measurement may be conducted for a samplewhose shape is different from the shape of a product or component thatis actually used, the measurement is to be conducted for a sample whichhas a thickness and a layer structure equal to the product that isactually used, when the thickness and the layer structure involve achange in the reflectivity.

Used in the present embodiment is a blue light emitting element having alight emission peak wavelength of 430 to 460 nm, and an upper surface ofthe conductive wiring 102 to be a bonding surface between the coveringmember 108 and the conductive wiring is formed of Cu so that thereflectivity is decreased in the region covered with the covering member108. As illustrated in FIG. 1, an opening 104 a of the light reflectinglayer is preferably positioned outside the covering member 108. In thepresent specification, the reflectivity refers to a reflectivity for thelight emission peak wavelength of a light emitting element used unlessotherwise particularly specified. When a wavelength conversion memberdescribed later is used, the light emission wavelength of a lightemitting element and the light emission wavelength of the wavelengthconversion member may be considered. This case is described in a secondembodiment described later.

The average reflectivity in the region of the base covered with thecovering member 108 is, for example, preferably 60% or less, morepreferably 50% or less, further preferably 40% or less. On the otherhand, the average reflectivity in the region of the base not coveredwith the covering member 108 is preferably 70% or more. Thereby, in aregion which is away from the light emitting element 105, thereflectivity can be made higher to give a light emitting device in whichluminance non-uniformity is improved.

Here, the difference between the average reflectivity in the region ofthe base covered with the covering member 108 and the averagereflectivity in the region of the base not covered with the coveringmember 108 is preferably 20% or more, more preferably 25% or more.Thereby, luminance unevenness can be improved.

The reflecting film formed on the second surface of the light emittingelement 105 may be a metal film or a dielectric multilayer film, forexample, distributed Bragg reflector (DBR) film. Thereby, light directedabove the light emitting element 105 is reflected by the reflecting film122 so that the quantity of light directly above the light emittingelement 105 can be reduced to provide batwing light distributioncharacteristics. The reflecting film can be directly formed on the lightemitting element 105, making a batwing lens unnecessary to reduce thethickness of the light emitting device.

The reflecting film 122 preferably has reflectivity dependent onincident angle of the emission wavelength of light from the lightemitting element 105. Specifically, the reflectivity of the reflectingfilm 122 is set to be lower for obliquely incident emission wavelengththan for perpendicularly incident emission wavelength. Accordingly, thechange in luminance directly above the light emitting element can bemoderated, thereby reducing occurrence of extreme darkness in a partdirectly above the light emitting element, i.e., a scotoma, for example.

Exemplification of Whole Configuration of Light Emitting Device

In the light emitting device according to the present embodiment, aplurality of covering members 108 may be arranged in a matrix form, eachcovering the light emitting element, as exemplified in FIG. 3. Thenumber and the arrangement of the light emitting elements used can beappropriately selected according to the purpose and the application ofthe light emitting device. Most of the region exposed from the coveringmember 108 is covered with the light reflecting layer 104.

For example, a wavelength conversion plate and a diffusing plate thatare in a form of a sheet or the like can be disposed above the lightemitting device configured as described above to produce a white lightsource of backlight. Wavelength-converted light enters the lightreflecting layer 104, and therefore, it is preferable that the lightreflecting layer 104 have a high reflectivity not only for the lightemission peak wavelength of the light emitting element but also for thelight emission wavelength of the wavelength-converted light.

According to the present embodiment, the light distributioncharacteristics of the light extracted from the light emitting element105 can be made into an ideal form, thereby improving luminancenon-uniformity when the light emitting device is used as a light sourcefor a backlight.

Second Embodiment

FIG. 4 illustrates a schematic sectional view of a light emitting deviceaccording to a second embodiment.

The light emitting device of the present embodiment is different fromthe light emitting device of the first embodiment in that a wavelengthconversion layer 109 is disposed between the light emitting element 105and the reflecting film 122 as illustrated in FIG. 4. Except thedifference, the light emitting device of the present embodiment can beconfigured in the same manner as in the first embodiment.

A part of the light emitted from the light emitting element 105 iswavelength-converted by the wavelength conversion layer 109. Further,light directed above the light emitting element 105 is reflected by thereflecting film 122, so that the quantity of light directly above thelight emitting element 105 can be reduced to provide batwing lightdistribution characteristics. The wavelength conversion layer 109 coversthe second surface and the plurality of lateral surfaces of the lightemitting element 105 as illustrated in FIG. 4. The wavelength conversionlayer 109 includes the reflecting film 122 on an upper surface of thewavelength conversion layer.

Also in the present embodiment, the reflectivity for the light emissionpeak wavelength of the light emitting element can be set in the samemanner as in the first embodiment in consideration of light whosewavelength is not converted, to reduce light extracted from directlyabove the light emitting element.

Further, the reflectivity for the peak wavelength of light whosewavelength is converted is also preferably set in the same manner inconsideration of light whose wavelength is converted. That is, theaverage reflectivity for the light emission peak wavelength of awavelength conversion member in the region of the base not covered withthe covering member is preferably set higher than the averagereflectivity for the light emission peak wavelength of a wavelengthconversion member in the region of the base covered with the coveringmember.

The wavelength conversion layer 109 is sufficient as long as it is, forexample, one that absorbs the light from the light emitting elementincluding a nitride semiconductor as a light emitting layer, andconverts the wavelength of the light into light having a differentwavelength. For example, a fluorescent substance-containing resinmaterial can be suitably used.

The light emitting device of the second embodiment, which is configuredas described above, can provide a white light source that enables ashort optical distance to an irradiation surface.

Third Embodiment

FIG. 5 illustrates a schematic sectional view of a light emitting deviceaccording to a third embodiment.

The light emitting device of the present embodiment is different fromthe light emitting device of the first embodiment in that the lightemitting element 105 has Lambertian light distribution characteristics,and a central portion on the upper surface of the covering member 108 isdepressed in order to allow the light emitted from the light emittingelement 105 to exhibit batwing light distribution characteristics. Inthe first embodiment, the reflecting film 122 is formed on the secondsurface of the light emitting element 105. In the present embodiment,however, the reflecting film does not exist, and the covering member 108includes a depression 134 in a portion directly above the light emittingelement 105 on a second surface side of the light emitting element.Regarding the other configuration, the light emitting device of thepresent embodiment can be configured in the same manner as the lightemitting device of the first embodiment.

In the light emitting device of the third embodiment configured asdescribed above, the covering member 108 includes the depression 134 onthe upper surface of the covering member to become a so-called batwinglens. The batwing lens can decrease the light intensity in a lateralsurface direction, for example, at a light distribution angle of 80° ormore by controlling the shape of the lens, because the batwing lenscontrols the light distribution characteristics by the entire reflectionand refraction of the light emitted from the upper surface of the lightemitting element, and the shape of the lens dominantly affects thequantity of light output to a lateral surface direction as compared withthe lens not having the depression 134, which is used together with thelight emitting element having the reflecting film and batwing lightdistribution.

Fourth Embodiment

FIG. 6 illustrates a schematic sectional view of a light emitting deviceaccording to a fourth embodiment.

The light emitting device of the present embodiment is different fromthe light emitting device of the third embodiment in that as illustratedin FIG. 6, a light absorbing member 107 is disposed on a bottom surfaceof the covering member 108 except an recess portion 136 provided tohouse the light emitting element 105 in a lower surface central portionof the covering member (i.e., a surface that is outside the recessportion 136 and is opposite to the upper surface of the base 120), andthe covering member is overlaid over the light emitting element 105 as asecondary lens. Regarding the other configuration, the light emittingdevice of the present embodiment can be configured in the same manner asin the third embodiment. This secondary lens is a so-called batwinglens.

The recess portion 136 is formed larger than the light emitting element105 to house the light emitting element 105. The light emitting element105 may be in direct contact with the covering member 108, and may be incontact with the covering member 108 with a bonding member such as aresin interposed between the light emitting element and the coveringmember. Alternatively, the light emitting element 105 may be in nocontact with the covering member 108.

The light absorbing member 107 can be formed on the bottom surface ofthe covering member 108 by, for example, coating the bottom surface witha light absorbing member described later.

The reflectivity of the light absorbing member 107 is preferably 50% orless, more preferably 40% or less for the light emission peak wavelengthof the light emitting element. When a material that absorbs only lightin a certain wavelength range is used as the light absorbing member, itis also possible to selectively reflect light in the other wavelengthranges. The light absorbing member 107 is preferably disposed lower thanthe light emitting element 105. This is to decrease the quantity oflight that enters the light absorbing member 107 after being emittedfrom the light emitting element. An inorganic material is preferablyused for the light absorbing member to prevent deterioration caused bylight. Specifically, there can be suitably used carbon black, triirontetraoxide, titanium black, or the like.

The light emitting device of the fourth embodiment, which is configuredas described above, can absorb reflected light in the secondary lens atthe bottom surface to reduce concentration and scattering of thereflected light.

Fifth Embodiment

FIG. 7 illustrates a schematic sectional view of a light emitting deviceaccording to a fifth embodiment.

In the present embodiment, the light reflecting layer 104 and the lightabsorbing member 107 are stacked between the upper surface of the baseand the lower surface of the covering member, and the light absorbingmember 107 is formed in a circular ring in a top view at a contact areabetween the outer edge of the covering member 108 and the upper surfaceof the base 120, as illustrated in FIG. 7. For example, as illustratedin FIG. 7, the light absorbing member 107 is formed so that an inner endthereof is disposed within the covering member 108, and an outer endthereof is positioned outside the covering member 108. Regarding theother configuration, the light emitting device of the present embodimentcan be configured in the same manner as the light emitting device of thefirst embodiment.

The present embodiment can also give the same effects as in the firstembodiment.

In the present embodiment, the conductive wiring on lateral sides of thelight emitting element 105 can be covered with an insulating material toreduce a failure risk of the light emitting element 105 caused by, forexample, static electricity.

Hereinafter, each of the embodiments is described in terms of materialsand the like suitable for the constituent members of the light emittingdevice.

Base 120

The base 120 is a member on which the light emitting element 105 ismounted, and includes, as illustrated in each of the drawings, theconductive wiring 102 for supplying power to the light emitting element105, and the support member 101 on which the conductive wiring 102 isdisposed and which insulates and separates the conductive wiring.

Support Member 101

Examples of the material for the support member 101 include ceramics andresins such as a phenol resin, an epoxy resin, a polyimide resin, a BTresin, polyphthalamide (PPA), and polyethylene terephthalate (PET).Especially, these resins are preferably selected for the material of thesupport member from the view point of low costs and easy molding. Thethickness of the support member can be appropriately selected, and thesupport member may be either a flexible substrate that can be producedby a roll-to-roll process, or a rigid substrate. The rigid substrate maybe a bendable thin rigid substrate. Alternatively, ceramics ispreferably selected for the material of the support member 101 in orderto produce a light emitting device excellent in heat resistance andlight resistance.

Examples of ceramics include alumina, mullite, forsterite, glassceramics, nitrides (e.g., AlN), carbides (e.g., SiC), and lowtemperature co-fired ceramics (LTCC).

When a resin is used for the material that constitutes the supportmember 101, a glass fiber or another inorganic filler such as SiO₂,TiO₂, or Al₂O₃ can be mixed in the resin to, for example, improve themechanical strength, decrease the coefficient of thermal expansion, andimprove the light reflectivity. The support member 101 is sufficient aslong as it can insulate and separate the pair of conductive wirings 102,and a so-called metal substrate obtained by forming an insulating layeron a metal member may also be used.

Conductive Wiring 102

The conductive wiring 102 is a member that is electrically connected toan electrode of the light emitting element 105 and that supplies anelectric current (power) from the outside. That is, the conductivewiring functions as an electrode for power distribution from theoutside, or a part of the electrode. Generally, the conductive wiring isformed in at least two (positive and negative) electrodes spaced apartfrom each other (e.g., 102 a and 102 b as illustrated in FIGS. 1 and 2).

The conductive wiring 102 is formed on at least an upper surface of thebase serving as a mounting surface for the light emitting element 105.The material for the conductive wiring 102 can be appropriately selectedaccording to, for example, the material used for the support member 101and the production method. For example, when ceramics is used for thematerial of the support member 101, the material for the conductivewiring 102 is preferably a material having a high melting temperature,which can be resistant to the firing temperature of a ceramic sheet, andhigh melting temperature metals such as tungsten and molybdenum arepreferably used. Further, the metal may be covered with one or moreother metal materials such as nickel, gold, or silver by, for example,plating, sputtering, or vapor deposition.

When a glass epoxy resin is used for the material of the support member101, the material for the conductive wiring 102 is preferably a readilyprocessable material. The conductive wiring 102 can be formed on onesurface or both surfaces of the support member by a method such as vapordeposition, sputtering or plating. A metal foil may be attached bypressing. A wiring portion can be masked by, for example, a printingmethod or photolithography and patterned into a predetermined shape byan etching process.

The material for the outermost surface of the conductive wiring 102 ispreferably selected with respect to the emission wavelength of lightfrom the light emitting element 105 used, in order to adjust the averagereflectivity in the region covered with the covering member.

For example, Cu or Au is preferably selected with respect to lighthaving a light emission peak wavelength of in a range of about 420 nm toabout 500 nm.

Bonding Member 103

The bonding member 103 is a member that fixes the light emitting element105 to the support member 101 or the conductive wiring 102. Examples ofthe bonding member include an insulating resin and an electricallyconductive member. In the case of flip-chip mounting as illustrated inFIG. 2, an electrically conductive member is used. Specific examples ofthe electrically conductive member include an Au-containing alloy, anAg-containing alloy, a Pd-containing alloy, an In-containing alloy, aPb—Pd-containing alloy, an Au—Ga-containing alloy, an Au—Sn-containingalloy, a Sn-containing alloy, a Sn—Cu-containing alloy, anSn—Cu—Ag-containing alloy, an Au—Ge-containing alloy, anAu—Si-containing alloy, an Al-containing alloy, a Cu—In-containingalloy, and a mixture of a metal and flux.

For the bonding member 103, a liquid, paste, or solid (sheet-shaped,block-shaped, powdery, or wire-shaped) member can be used. The state ofthe member can be appropriately selected according to, for example, thecomposition of the member and the shape of the base. The bonding member103 may be formed of a single member or a plurality of members incombination. When the bonding member does not serve for, together withfixation, electrical connection to the conductive wiring 102, wire,apart from fixation, may be used to electrically connect an electrode ofthe light emitting element 105 to the conductive wiring 102.

Light Reflecting Layer 104

The conductive wiring 102 is preferably covered with the lightreflecting layer 104 except a part which electrically connects to thelight emitting element 105 or other components. That is, as illustratedin FIG. 2, a resist may be disposed on the base 120 to insulativelycover the conductive wiring 102, and the light reflecting layer 104 canbe functioned as the resist. By adding a white-based filler in a resinmaterial described later, the light emitting device can be less likelyto cause leakage and absorption of light, thereby improving the lightextraction efficiency.

The resin material in which the white-based filler is contained issufficient as long as it is a material that is less likely to absorb thelight from the light emitting element and is insulative. There can beused, for example, epoxy resin, silicone resin, modified silicone resin,a urethane resin, an oxetane resin, acrylic resin, polycarbonate resin,and a polyimide resin. These may be used alone or in combination.Examples of the white-based filler include oxides such as SiO₂, Al₂O₃,Al(OH)₃, MgCO₃, TiO₂, ZrO₂, ZnO₂, Nb₂O₅, MgO, Mg(OH)₂, SrO, In₂O₃, TaO₂,HfO, SeO, and Y₂O₃; nitrides such as SiN, AN, and AlON; and fluoridessuch as MgF₂. These may be used alone or in mixture.

Light Emitting Element 105

For the light emitting element 105, a publicly known one can be used.For example, a light emitting diode is preferably used as the lightemitting element 105.

A wavelength of the light emitting element 105 can be appropriatelyselected. For example, one including a nitride semiconductor(In_(x)Al_(y)Ga_(1-x-y)N, 0≤X, 0≤Y, X+Y≤1) can be used as a blue orgreen light emitting element. For example, GaAlAs and AllnGap can beused as a red light emitting element. Further, a semiconductor lightemitting element can also be used, which is made of a material otherthan the materials described above. The composition, the emission color,the size, the number, and the like of the light emitting element usedcan be appropriately selected according to the purpose.

When the light emitting device includes a wavelength conversionmaterial, preferable examples of the light emitting element include anitride semiconductor (In_(x)Al_(y)Ga_(1-x-y)N, 0≤X, 0≤Y, X+Y≤1) whichcan emit short-wavelength light capable of efficiently exciting thewavelength conversion material. The emission wavelength can be variouslyselected by the material for a semiconductor layer and the mixedcrystallinity of the material. The light emitting element may includepositive and negative electrodes on the same surface side, or mayinclude positive and negative electrodes on difference surfaces.

The light emitting elements of the present embodiments include asubstrate and a semiconductor layer stacked on the substrate. Thissemiconductor layer includes an n-side semiconductor layer, an activelayer, and a p-side semiconductor layer formed in this order. The n-sidesemiconductor layer has an n-electrode formed therein, and the p-sidesemiconductor layer has a p-electrode formed therein. The substrate inthe present embodiments is a sapphire substrate that has a reflectingmirror made of a dielectric multilayer film formed on a surface oppositeto the semiconductor layer.

The electrodes of these light emitting elements 105 are flip-chipmounted on the conductive wiring 102 on the surface of the supportmember with the bonding member 103 interposed between the electrodes andthe conductive wiring as illustrated in FIG. 2, and a surfacesubstantially perpendicular to a surface on which the electrodes areformed, i.e., a light-transmissive sapphire substrate lateral surface,is set to be a light extraction surface. The light emitting element 105is disposed so as to straddle the two (positive and negative) conductivewirings 102 electrically separated from each other, and is bonded by thebonding member 103. Examples of the method of mounting the lightemitting element 105 include a mounting method using a bump, as well asa mounting method using a solder paste.

For the light emitting element, a compact packaged product can also beused.

Underfill Material 106

The underfill material 106 is formed between the light emitting element105 and the support member 101. The underfill material 106 may contain afiller or a pigment for the purpose of approximating the coefficient ofthermal expansion of the underfill material to the coefficient ofthermal expansion of the light emitting element, and the purpose ofreduction in scattering and reflecting the light from the light emittingelement 105 by the support member 101.

The material of the underfill material 106 is sufficient as long as itis less likely to be deteriorated by the light from the light emittingelement. There can be used, for example, epoxy resin, silicone resin,modified silicone resin, a urethane resin, an oxetane resin, acrylicresin, polycarbonate resin, and a polyimide resin.

When the filler or pigment contained in the underfill material 106 is afiller or pigment that absorbs light of the emission wavelength, lightbecomes much less likely to be reflected, so that scattering of lightcan be reduced.

An inorganic compound is preferably used for the light absorbingmaterial to reduce deterioration caused by light. Here, the reflectivityof the filler is preferably 50% or less, more preferably 40% or lesswith respect to the emission wavelength of light.

The particle size of the filler is preferably 1 nm or more and 10 μm orless. With the particle size of the filler in this range, the resinflowability of the underfill material becomes good, thereby enablingsmoothly covering of even a narrow gap. The particle size of the filleris preferably 100 nm or more and 5 μm or less, more preferably 200 nm ormore and 2 μm or less. The shape of particles of the filler may bespherical or scale-shaped.

When the underfill material does not have transmissivity, it ispreferable that the lateral surfaces of the light emitting element isnot covered with the underfill material by appropriately selecting andadjusting a disposition location and the material of the underfill. Thisis to enable the lateral surfaces of the light emitting element tosecurely serve as light extraction surfaces.

Covering Member 108

The covering member in the present embodiments is a member that isdisposed on the support member to cover the light emitting element sothat the light emitting element is protected from an externalenvironment and the light output from the light emitting element isoptically controlled.

Examples of the material for the covering member 108 includelight-transmissive resins such as an epoxy resin, a silicone resin and amixed resin of an epoxy resin and a silicone resin; and glass.Especially, the silicone resin is preferably selected in considerationof light resistance and ease of molding.

The top of the covering member 108 is preferably at a height of 2 mm orless from the upper surface of the base 120. Thereby, the opticaldistance to the irradiation surface can be reduced.

Further, in the covering member 108, the height H viewed from a lateralsurface where the width W appears the smallest as illustrated in FIG. 2is preferably 0.5 times or less the width. Thereby, wide lightdistribution can be obtained as compared with the case in which theheight is higher than 0.5 times the width.

The light-transmissive rein can contain a wavelength conversion materialthat absorbs the light from the light emitting element and emits lightof a wavelength different from the wavelength of the output light fromthe light emitting element, and a diffusing agent that diffuses thelight from the light emitting element. A coloring agent can also becontained in accordance with the emission color of the light emittingelement.

It is preferable that the covering member 108 do not have lightdiffuseness from the viewpoint of reducing the light intensity directlyabove the light emitting element. However, a minimal light diffusingagent that is required to give thixotropy necessary for molding may beadded to the covering member.

The covering member 108 can be formed so as to cover the light emittingelement by compression molding or injection molding. In addition, theviscosity of the material for the covering member 108 is optimized fordropping or drawing on the light emitting element 105, so that theshapes illustrated in the drawings can be formed by the surface tensionof the material itself.

When the dropping or drawing method is used, a mold is not required,thereby enabling formation of the covering member by a simpler method.As the method of adjusting the viscosity of the material for thecovering member according to such a forming method, the fluorescentmaterial and the diffusing agent that are described above can also beutilized other than utilizing the original viscosity of the material.

Fluorescent Material

As the fluorescent material, there can be used, for example, a nitridefluorescent material and an oxynitride fluorescent material that aremainly activated by lanthanoids such as Eu and Ce. Specifically, thefluorescent material is preferably at least one selected from thematerials described in (D1) to (D3) into which the materials are roughlycategorized.

(D1) Fluorescent materials, such as alkaline earth halogen apatite,alkaline earth metal halogen borate, alkaline earth metal aluminate,alkaline earth metal sulfide, alkaline earth metal thiogallate, alkalineearth metal silicon nitride and germanate, which are mainly activated bylanthanoids such as Eu and transition metal elements such as Mn.

(D2) Fluorescent materials, such as rare earth aluminate, rare earthsilicate, and alkaline earth metal rare earth silicate, which are mainlyactivated by lanthanoids such as Ce.

(D3) Fluorescent materials, such as an organic or organic complex, whichare mainly activated by lanthanoids such as Eu.

Especially, an yttrium aluminum garnet (YAG) based fluorescent materialis preferable, which is a rare earth aluminate fluorescent materialmainly activated by lanthanoids such as Ce in (D2) described above. TheYAG based fluorescent material is represented by the followingcomposition formulate (D21) to (D24), for example.

Y₃Al₅O₁₂:Ce  (D21)

(Y_(0.8)Gd_(0.2))₃Al₅O₁₂:Ce  (D22)

Y₃(Al_(0.8)Ga_(0.2))₅O₁₂:Ce  (D23)

(Y,Gd)₃(Al,Ga)₅O₁₂:Ce  (D24)

Alternatively, a part or all of Y may be substituted with Tb, Lu, or thelike, for example. Specifically, the composition formula may beTb₃Al₅O₁₂: Ce, Lu₃Al₅O₁₂: Ce, and the like. A fluorescent material canalso be used, which is other than the above-described fluorescentmaterials and has a similar performance, action and effect as those ofthe above-described fluorescent materials.

The covering member contains a wavelength conversion material to give alight emitting device capable of outputting light having a desiredwavelength.

Hereinafter, examples according to an embodiment of the presentinvention are described in detail. It is indisputable that theembodiment of the present invention is not limited only to the examplesbelow.

Example 1

FIGS. 1 and 2 illustrate a schematic top view and a schematic sectionalview of a light emitting device of Example 1.

On a support member 101 of the present example, a light emitting element105 is flip-chip mounted so as to straddle a pair of positive andnegative conductive wirings 102 a and 102 b provided on the supportmember with a bonding member 103 interposed between the light emittingelement and the pair of conductive wiring lines, as illustrated inFIG. 1. A light reflecting layer 104 is formed in a region of aconductive wiring 102 which does not require electrical connection. Alight-transmissive underfill material 106 is formed under and on alateral surface of the light emitting element 105, and a covering member108 is formed so as to directly cover the underfill material 106.

In the present example, a glass epoxy base material is used for thesupport member 101, a Cu material having a thickness of 35 μm is usedfor the conductive wiring 102, and an epoxy white solder resist is usedfor the light reflecting layer 104.

The light emitting element 105 can employ a nitride blue LED which is asubstantially square having each side of 600 μM and has a thickness of150 μm, and a dielectric multilayer film is formed on an upper surfacethereof. The underfill material 106 can employ a silicone resin. Thecovering member 108 can employ a silicone resin and is formed into asubstantial dome shape.

Although it is preferable that the covering member 108 in the presentexample do not contain light diffuseness, a silica based nanofiller isadded to give thixotropy to the covering member.

The ratios of the areas of the conductive wiring 102 and a grooveportion 130 that are in contact with the covering member 108 are about90% and about 10%, respectively, relative to the bottom area of thecovering member 108. The reflectivity of the conductive wiring is about50% for the light emission wavelength of the light emitting element, andthe reflectivity of the groove portion is about 80% for the emissionwavelength of light from the light emitting element. The averagereflectivity is thus about 53% in consideration of the ratio of theareas in the region covered with the covering member 108. On the otherhand, the reflectivity of the light reflecting layer 104 is about 80%for the emission wavelength of light from the light emitting element.

Example 2

FIG. 8 illustrates a schematic top view of a light emitting device ofExample 2, and FIG. 9 illustrates a schematic sectional view taken alongthe line B-B in FIG. 8. In the light emitting device of Example 2, theratio of the area of the conductive wiring 102 in contact with thecovering member 108 is changed from the ratio in the light emittingdevice of Example 1. In the light emitting device of Example 2, thelight reflecting layer 104 is also disposed under the covering member108, and the conductive wiring is exposed from the light reflectinglayer 104 only in the vicinity of the light emitting element. An opening104 a of the light reflecting layer is positioned under the coveringmember 108.

In the light emitting device of Example 2, the ratios of the areas ofthe conductive wiring, the light reflecting layer 104, and the grooveportion 130 that are in contact with the covering member 108 are 23%,72%, and 5%, respectively, relative to the bottom area of the coveringmember 108. The reflectivity of the conductive wiring is 50% for theemission wavelength of the light emitting element, and the reflectivityof the light reflecting layer and the groove portion is 80% for theemission wavelength of the light emitting element. The averagereflectivity is thus 73% in consideration of the ratio of the areas inthe region covered with the covering member 108.

FIG. 10 illustrates a light distribution characteristic graph of thelight emitting device of Example 1, and FIG. 11 illustrates a lightdistribution characteristic graph of the light emitting device ofExample 2. In the light emitting device of Example 2, the relative lightintensity is reduced only to about 0.47 in a region at a lightdistribution angle of 0°, whereas in Example 1 in which the averagereflectivity is set to be 60% or less in the region covered with thecovering member 108, the relative light intensity is reduced to about0.35 in a region where the relative light intensity becomes low so thatit is understood that the light intensity in an upper surface directioncan be adequately decreased. That is, the reflectivity on the surface ofa part in contact with the covering member can be adjusted to obtaindesired light distribution characteristics.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A light emitting device comprising: a basecomprising: a support having a support surface; and a conductive wiringprovided on the support surface; a light emitting element mounted on theconductive wiring and the support surface to be electrically connectedto the conductive wiring, the light emitting element comprising: asemiconductor layer provided on the conductive wiring and the supportsurface; and a sapphire substrate provided on the semiconductor layeropposite to the support surface; a reflecting film provided on thesapphire substrate to sandwich the sapphire substrate between thesemiconductor layer and the reflecting film, a light emitted from thesemiconductor layer being configured to be extracted from the sapphiresubstrate between the semiconductor layer and the reflecting film; and alight-transmissive covering member provided on the support surface tocover the light emitting element and a covered region on the supportsurface except for an uncovered region on the support surface, a heightof the light-transmissive covering member viewed in a direction in whicha width of the light-transmissive covering member appears smallest being0.5 times or less of the width of the light-transmissive coveringmember, an average reflectivity in the uncovered region of the base withrespect to a peak emission wavelength of light emitted from the lightemitting element being higher than an average reflectivity in thecovered region of the base with respect to the peak emission wavelengthof light.
 2. The light emitting device according to claim 1, wherein theaverage reflectivity of the covered region on the base is 60% or lesswith respect to the peak emission wavelength of light emitted from thelight emitting element.
 3. The light emitting device according to claim1, wherein the average reflectivity of the uncovered region on the baseis 70% or more with respect to the peak emission wavelength of lightemitted from the light emitting element.
 4. The light emitting deviceaccording to claim 1, wherein the conductive wiring has an outermostsurface containing Cu.
 5. The light emitting device according to claim1, wherein the light-transmissive covering member is in direct contactwith the base.
 6. The light emitting device according to claim 1,wherein a height between the conductive wiring and the top of thelight-transmissive covering member is 2 mm or less in the heightdirection.
 7. The light emitting device according to claim 1, whereinthe covering member includes a light absorbing portion, which covers atleast a portion of the covered region on the base.
 8. The light emittingdevice according to claim 1, wherein the covering member includes alight absorbing portion on the bottom of the covering member.
 9. Thelight emitting device according to claim 1, wherein the reflecting filmhas angular dependence of reflectivity.
 10. The light emitting deviceaccording to claim 1, wherein the reflecting film is a dielectricmultilayer film.
 11. The light emitting device according to claim 1,wherein the light-transmissive covering member having a bottom facingthe base and a top opposite to the bottom in a height direction along aheight of the light emitting device, wherein the height of thelight-transmissive covering member is a length from the bottom to thetop in the height direction, wherein the light-transmissive coveringmember has maximum widths in respective width directions perpendicularto the height direction as viewed in arbitrary sight directionsperpendicular to the height direction and the respective widthdirections, and wherein the height of the light-transmissive coveringmember is 0.5 times or less of a minimum value of the maximum widths.